1. Field of the Invention
The present invention relates to an extended interface device. More particularly, the invention relates to an extended interface device which is connected to an OA (office automation) apparatus, such as a printer, a copier, a facsimile apparatus, a scanner or the like, and provides the OA apparatus with a new interface function by being supplied with electric power from the main body of the OA apparatus.
2. Description of the Related Art
Recent diffusion of networks, such as LAN's (local area networks) and the like, is remarkable, and, for example, data sharing by a plurality of clients, such as personal computers, work stations and the like, and sharing of input/output apparatuses, such as printers, scanners and the like are also common. This trend extends even to business machines, such as fascimile apparatuses and the like. In accordance with development of digital business machines, the utilization of the input/output function of such a business machine as a printer, a scanner or the like via a network is effected.
Under such circumstances, network interface devices for providing OA apparatuses, such as printers, copiers, facsimile apparatuses, scanners and the like, with a network function of a LAN or the like have been put on the market by various suppliers. Among these devices, there are network interface devices, each connected to an extended interface provided in the main body of an OA apparatus and supplied with electric power from the main body of the OA apparatus via the interface. Extended interface devices for providing the connected OA apparatus with a new interface function other than the network function have also been devised.
The above-described network interface device, which is connected to an extended interface connector of an OA apparatus, such as a printer, a copier, a facsimile apparatus, a scanner or the like, and supplies the OA apparatus with a network interface of a LAN or the like, by being supplied with electric power from the main body of the OA apparatus, has the following problems.
First, it is desirable that unified extended-interface specifications are provided for network interface devices and various kinds of OA apparatuses, and a network interface device of one type deals with various kinds of OA apparatuses. Actually, however, various kinds of OA apparatuses to be dealt with have different specifications. The processing capability requested to a network interface device and the current capacity which can be supplied to the network interface device via an extended interface also differ depending on the OA apparatus.
For example, suppose that a low-speed printer having a printing speed of 4 copies/min and a high-speed printer having a printing speed of 40 copies/min have the same extended interface, and the two printers are dealt with by a network interface device of one type. The high-speed printer requests a high-speed network interface in order to utilize its high printing speed. On the other hand, the low-speed printer requests only a network interface corresponding to its low printing speed, and does not require a high-speed processing capability requested by the high-speed printer for the network interface device. In general, the amount of current suppliable to an extended interface is smaller as the speed of an OA apparatus is lower, because there is a limitation in the space for the power supply. On the other hand, current consumption is larger as the processing capability of a network interface device is higher.
Accordingly, for a network interface device having a high processing capability corresponding to a high-speed copier, the current capacity suppliable from a low-speed printer is insufficient. As a result, it is necessary to prepare network interface devices of two types having the same functions except for their speed.